PG&E transmission towers, including the one at right that reportedly malfunctioned minutes before the Camp Fire was first reported above Poe Dam, stand on a ridge above Pulga, Calif., Thursday, Dec. 6, 2018. Investigators have taken equipment from the tower as evidence. (Karl Mondon/Bay Area News Group)

SAN FRANCISCO — With wildfires ravaging California year after year, the state Public Utilities Commission voted unanimously Thursday to begin strengthening rules that govern when utilities should turn off power lines in high winds to keep them from sparking blazes, and to improve the technology used to make those decisions.

But commissioners warned it could be a long process , and that other safety precautions like vegetation management around power lines must remain a priority.

“We can’t keep doing the same thing,” commission Chairman Michael Picker said. But he cautioned, “I don’t think we’ll have a perfect set of rules right away. We have to learn how to do this.”

The commission’s action comes as investigators focus on whether a transmission tower failed in high winds last month and ignited the Camp Fire in Butte County, the most destructive blaze in state history. It killed 86 people and destroyed nearly 19,0000 structures. PG&E had warned customers for two days that it might shut down power on Nov. 8, the day the fire started, because of forecasts for high winds, low humidity and other high fire conditions, but never did.

While utilities already have the authority to turn off power lines — an option PG&E has used once this fall in the wake of last year’s devastating North Bay fires — improved rules could set exact criteria dictating when power must be interrupted. Any rules will also require new technology to help in decision making and understanding the impacts of shut downs, Picker and others said. PG&E announced this week that it would add 1,200 new weather stations and several hundred high definition cameras in high fire-risk areas by 2022.

But with a warming climate and droughts creating ideal conditions for the massive wildfires that have scorched the state and killed scores of people the last two years — some caused by failing utility poles and wires — “we can’t not take action,” Commissioner Clifford Rechtschaffen said.

Many factors go into the decisions to interrupt service, Picker said, and more and better data is needed at critical moments. Wind speeds, he noted, are often recorded at mountain tops, but it can be “wind gusts in the bottom of canyons” that damage power lines and start fires.

The PUC’s safety division recommended commissioners develop “best practices (for) and ensuring an orderly and effective set of criteria for evaluating de‑energization programs” and whether it should “develop metrics” that would govern when utilities should shut off power, according to staff reports.

Picker pointed to San Diego Gas and Electric as an example of a utility that has an advanced system of weather censors to help guide decisions whether to interrupt power or not, and said it could be useful in developing a pilot program.

But, that utility provides power just to San Diego County — an area dwarfed by PG&E’s vast Northern California service area that covers diverse terrain from the coast to hot inland areas and remote forests and mountain ranges with wide-ranging weather conditions.

PG&E said previously that it did not consider shutting down the high-voltage lines supported by the failed tower. Under the utility’s policy adopted this summer, PG&E excludes shutting off lines carrying 115,000 volts or higher, although the CPUC has no rules preventing that. PG&E said previously that it adopted that rule because shutting down such a line would likely affect more customers than intended. The CPUC, which is investigating PG&E’s role in the fire, is looking into its decision to not turn off power, a spokeswoman has said.

The commissioners acknowledged that the impact of shutdowns on vulnerable customers has to be considered when such decisions are made. Depending how electricity is routed, people not in an area of fire danger might suffer shutdowns in order to protect others, they said.

A shutdown “is a very significant event,” Rechtschaffen said. It can affect people who rely on medical equipment that requires electricity and in other ways, he said. “It disrupts and endangers their lives.”

Picker indicated that utilities could retain some discretion in making decisions to interrupt power. “We should not practice regulatory overreach,” he said.

Cal Fire has also collected pieces of the tower that fell apart before the blaze as evidence. In a report to the CPUC late Tuesday, PG&E wrote that it found a hook designed to hold up power lines on the tower was broken before the fire, and that the pieces showed wear.

Lawyers suing the utility have said the tower should have withstood the high winds without damage had it been properly maintained.

Thomas Peele is a Pulitzer Prize winning investigative reporter on the Bay Area News Group's regional team. He has worked at newspapers, including Newsday, for 34 years in California and elsewhere. Peele focuses on government accountability, public records and data, often speaking about transparency laws publicly.

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